Controlled freezing of biological tissue, such as skin tissue, can produce various effects. Certain tissue freezing procedures and devices, such as conventional cryoprobes, can cause severe freezing of tissue and generate cellular damage. It has been observed that moderate degrees of freezing can produce particular effects, such as affecting the expression of skin pigmentation.
There is a demand for cosmetic products that can lighten the appearance of skin or otherwise controllably affect skin pigmentation. For example, it may be desirable to lighten the overall complexion or color of a region of skin to alter the general appearance for cosmetic reasons. Also, lightening of particular hyperpigmented regions of skin, such as large freckles, ‘caféau lait’ spots, melasma, or dark circles under the eyes that may result from excessive local amounts of pigment in the skin, may also be desirable for cosmetic reasons. Hyperpigmentation can result from a variety of factors such as UV exposure, aging, stress, trauma, inflammation, etc. Such factors can lead to an excess production of melanin, or melanogenesis, in the skin by melanocytes, which can lead to formation of hyperpigmented areas. Such hyperpigmented areas are typically located within the epidermis; however, they can also result from excess melanin deposited within the dermis. Many topical formulations are being marketed that claim to lighten age spots and reduce the effects of such hyperpigmentation. However, these cosmetic formulations may have questionable effectiveness.
Hypopigmentation of skin tissue has been observed as a side effect in response to temporary cooling or freezing of the tissue, such as may occur during cryosurgery procedures. Loss of pigmentation following skin cooling or freezing may result from decreased melanosomes production, destruction of melanocytes, or inhibited transfer of melanosome into the keratinocytes in the lower region of the epidermal layer. The resultant hypopigmentation may be long-lasting or permanent. It has also been observed that some of these freezing procedures can generate regions of hyperpigmentation of skin tissue.
Accordingly, there may be a need to provide methods and apparatus that can provide controlled freezing of skin or other tissue, and gradual lightening of skin tissue that can address and/or overcome at least some of the deficiencies or issues described herein above.